1. Field of the Invention
The present invention relates to a vibration sensor film for detecting a particular mode of vibration, a vibration actuator film for generating the particular mode of vibration, a vibration reduction film for reducing the particular mode of vibration, and a multilayer film using the vibration sensor film, the vibration actuator film, or the vibration reduction film.
2. Description Related to the Prior Art
A piezoelectric sensor and a piezoelectric actuator that use a piezoelectric polymer film are conventionally known. In this piezoelectric sensor or the piezoelectric actuator, in general, the piezoelectric polymer film made of PVDF (polyvinylidene fluoride) is cut into a desired shape, and is glued on an object to be detected or driven.
In recent years, it is proposed to use the piezoelectric sensor for vibration detection, and use the piezoelectric actuator for vibration generation. According to Japanese Patent Laid-Open Publication No. 5-172839, for example, a piezoelectric vibration sensor is constituted of a base attached to an object to be measured, a sensing section, and a load body fixed on the sensing section. The sensing section includes a film-shaped piezoelectric body, which includes a piezoelectric film and mesh electrodes provided on both surfaces of the piezoelectric film, and support plates fixed on both surfaces of the piezoelectric body. The load body imposes on the piezoelectric film a load the weight of which depends on a vibration, and causes distortion of the piezoelectric film. Upon vibration of the object to be measured, voltage is outputted from the mesh electrodes in accordance with the distortion of the piezoelectric film, and thus the vibration is detected.
According to Japanese Patent Laid-Open Publication 7-209072, a vibration intensity detector is constituted of a rectangular polymeric piezoelectric film (piezoelectric polymer film), a plurality of electrodes, and a protection film for covering the piezoelectric polymer film and the electrodes. The electrodes are provided on both surfaces of the piezoelectric polymer film at regular intervals in a longitudinal direction so as to be opposed to each other. This detector is easily attached to an object to be measured by an adhesive, and gets output voltage in response to deformation of the object to be measured.
In the piezoelectric vibration sensor according to the Japanese Patent Laid-Open Publication No. 5-172839, the support plates are disposed on the mesh electrodes, and make it difficult to pull out wiring of the mesh electrodes. Also, the base and the support plates prevent reduction in the thickness of the piezoelectric vibration sensor.
The vibration intensity detector according to the Japanese Patent Laid-Open Publication No. 7-209072 is attached to the object to be measured for use. Thus, an attachment position error of the detector seriously affects its performance. Furthermore, the thickness of the detector attached to the object prevents integration of the object into a device, or causes upsizing of the device.
In addition, when the conventional piezoelectric sensor is attached to a random area of a plate, the piezoelectric sensor detects various modes of vibration in a mixed manner. As a result, if the piezoelectric actuator is operated to counteract the detected vibration, there is a case where the piezoelectric actuator generates an unnecessary mode of vibration, and contrarily increases the vibration.
Therefore, if a piezoelectric sensor can detect a particular mode of vibration and a piezoelectric actuator can generate the particular mode of vibration, the detection accuracy of the piezoelectric sensor and the driving accuracy of the piezoelectric actuator will be significantly improved. The above publications, however, do not consider it.